The present invention relates to a new and improved coupling which is utilized to interconnect a pair of conduits. More specifically, the invention relates to a coupling having a socket assembly with a heat fusible element which fuses upon exposure to excessive heat to enable a plug to be withdrawn from the socket assembly.
During the use of gas appliances, such a cooking stoves and other devices, there is an ever present danger of a fire which will travel through the conduits to a source of flammable gas. In order to prevent this from happening, couplings have been provided with a safety cutoff which closes a valve to block a flow of gas to the appliance upon heating of the coupling. Known couplings which may be used in such an environment and having safety cutoff devices which respond to exposure of the coupling to excessive heat are disclosed in U.S. Pat. Nos. 3,245,423; 3,532,101; 4,280,523.
A coupling disclosed in U.S. Pat. No. 4,280,523 includes a plug which is telescopically received in a socket assembly. The socket assembly has a plurality of locking elements which engage an annular collar or ring disposed on a plug body to hold the plug and socket assembly against movement relative to each other. When the coupling is heated to a predetermined temperature, the plug body is released from the collar and is ejected from the socket assembly. At the same time, a valve in the socket assembly is closed to block the flow of gas or other fluid through the coupling.
In order to release the plug body of U.S. Pat. No. 4,280,523 from the collar when the coupling is heated to the relatively high temperature, a body of fusible material is utilized to connect the collar with the plug body. When a fire or other condition heats the coupling to a predetermined temperature, the body of material fuses so that it is no longer effective to hold the collar and plug body against movement relative to each other. When this occurs, a spring in the socket assembly moves a valve to a closed condition and causes the valve to push the plug body out of the socket assembly. When this happens, both the fluid connection and the physical connection between the two conduits is interrupted to prevent further spreading of a fire.